Snow depth, sea ice thickness and interface temperatures derived from measurements of SIMBA buoy 2023T99

The Snow and Ice Mass Balance Array (SIMBA) is a thermistor string type IMB (Jackson et al., 2013) which measures the environmental temperature SIMBA-ET and a temperature change around the thermistors after a weak heating is applied to each sensor (SIMBA-HT). SIMBA 2023T99 (a.k.a. AWI_0907) is an autonomous instrument that was installed on drifting sea ice in the Arctic Ocean (Polarstern PS138-Arcwatch 2023) as part of the project Sea Ice Physics @ AWI (AWI_SeaIce). Its thermistor chain is 5 m long, and equipped with 241 thermistors (Maxim Integrated DS28EA00) at a spacing of 2 cm. Based on a manual classification method, the SIMBA-ET and SIMBA-HT were processed to obtain snow depth and ice thickness (smoothed with a 3-day running mean), as well as the thermistor number, the vertical position Z relative to the snow-ice interface and the measured SIMBA-ET at each detected interface (atmosphere-snow, snow-ice and ice-ocean) for the period between 2023-08-26T08:00:17 and 2024-02-29T20:00:18. To do this, we combined two derivatives of measured temperatures (the ET vertical gradient and HT rise ratio) to reduce the detection uncertainty of all interfaces considered. The snow or ice surface, consequentially the snow depth, is determined by the ET vertical gradient. Potential formation of snow ice is not explicitly considered in this data set, but may occur as depicted by vertical changes of the snow-ice interface position. The ice-ocean interface is usually determined using the HT rise ratio and serves as the lower limit for ice thickness. Overall, the accumulated error is 2 to 4 times the sensor spacing for both the snow depth and ice thickness. For interface temperatures, individual sensors in the chain measure with a temperature resolution of 0.0625°C, with the overall accuracy landing in the range of ± 2°C (Jackson et al., 2013). After the snow cover has melted, negative values for snow depth may indicate the onset of ice surface melt.

雪冰质量平衡阵列（Snow and Ice Mass Balance Array, SIMBA）是一款热敏电阻串式冰质量平衡传感器（Ice Mass Balance, IMB，Jackson等，2013），可开展两项测量：一是环境温度（SIMBA-ET），二是对每个传感器施加弱加热后热敏电阻周围的温度变化（SIMBA-HT）。SIMBA 2023T99（又名AWI_0907）是一款自主观测仪器，作为阿尔弗雷德·魏格纳研究所海冰物理项目（Sea Ice Physics @ AWI, AWI_SeaIce）与极星号Polarstern PS138航次Arcwatch 2023任务的一部分，被部署于北冰洋浮冰上。该仪器的热敏电阻链全长5米，搭载241个Maxim Integrated DS28EA00型号热敏电阻，间距为2厘米。基于人工分类方法，研究人员对SIMBA-ET与SIMBA-HT数据进行处理，得到雪深与冰厚数据（已通过3天滑动平均进行平滑），同时提取2023年8月26日08时00分17秒至2024年2月29日20时00分18秒期间，各检测界面（大气-雪面、雪冰界面与冰海界面）对应的热敏电阻编号、相对于雪冰界面的垂直位置Z，以及各界面的实测SIMBA-ET值。处理过程中，我们结合实测温度的两个导数项（ET垂直梯度与HT上升率），以降低所考虑的所有界面的检测不确定性。雪/冰表面（进而雪深）由ET垂直梯度确定。本数据集未明确考虑雪冰的潜在形成过程，但该过程可通过雪冰界面位置的垂直变化得以体现。冰海界面通常通过HT上升率确定，作为冰厚的下限。总体而言，雪深与冰厚的累积误差为传感器间距的2至4倍。界面温度测量方面，该热敏电阻链中的单个传感器温度分辨率为0.0625℃，整体精度范围为±2℃（Jackson等，2013）。当积雪消融后，雪深的负值可指示冰面融化的开始。